linux-kernel - [PATCH v10 13/38] x86/cpu: Add X86_CR4

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Date:   Wed, 13 Sep 2023 21:47:40 -0700
From:   Xin Li <xin3.li@...el.com>
To:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-edac@...r.kernel.org, linux-hyperv@...r.kernel.org,
        kvm@...r.kernel.org, xen-devel@...ts.xenproject.org
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        luto@...nel.org, pbonzini@...hat.com, seanjc@...gle.com,
        peterz@...radead.org, jgross@...e.com, ravi.v.shankar@...el.com,
        mhiramat@...nel.org, andrew.cooper3@...rix.com,
        jiangshanlai@...il.com
Subject: [PATCH v10 13/38] x86/cpu: Add X86_CR4_FRED macro

From: "H. Peter Anvin (Intel)" <hpa@...or.com>

Add X86_CR4_FRED macro for the FRED bit in %cr4. This bit must not be
changed after initialization, so add it to the pinned CR4 bits.

Signed-off-by: H. Peter Anvin (Intel) <hpa@...or.com>
Tested-by: Shan Kang <shan.kang@...el.com>
Signed-off-by: Xin Li <xin3.li@...el.com>
---

Changes since v9:
* Avoid a type cast by defining X86_CR4_FRED as 0 on 32-bit (Thomas
  Gleixner).
---
 arch/x86/include/uapi/asm/processor-flags.h | 7 +++++++
 arch/x86/kernel/cpu/common.c                | 5 ++---
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/uapi/asm/processor-flags.h b/arch/x86/include/uapi/asm/processor-flags.h
index d898432947ff..f1a4adc78272 100644
--- a/arch/x86/include/uapi/asm/processor-flags.h
+++ b/arch/x86/include/uapi/asm/processor-flags.h
@@ -139,6 +139,13 @@
 #define X86_CR4_LAM_SUP_BIT	28 /* LAM for supervisor pointers */
 #define X86_CR4_LAM_SUP		_BITUL(X86_CR4_LAM_SUP_BIT)
 
+#ifdef __x86_64__
+#define X86_CR4_FRED_BIT	32 /* enable FRED kernel entry */
+#define X86_CR4_FRED		_BITUL(X86_CR4_FRED_BIT)
+#else
+#define X86_CR4_FRED		(0)
+#endif
+
 /*
  * x86-64 Task Priority Register, CR8
  */
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 317b4877e9c7..42511209469b 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -400,9 +400,8 @@ static __always_inline void setup_umip(struct cpuinfo_x86 *c)
 }
 
 /* These bits should not change their value after CPU init is finished. */
-static const unsigned long cr4_pinned_mask =
-	X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_UMIP |
-	X86_CR4_FSGSBASE | X86_CR4_CET;
+static const unsigned long cr4_pinned_mask = X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_UMIP |
+					     X86_CR4_FSGSBASE | X86_CR4_CET | X86_CR4_FRED;
 static DEFINE_STATIC_KEY_FALSE_RO(cr_pinning);
 static unsigned long cr4_pinned_bits __ro_after_init;
 
-- 
2.34.1